Phonographic recording-stylus.



T. A. EDISON.

PHONOGRAPHIC RECORDING STYLUS. APPLICATION FILED JAN. 3, 1967. RENEWED 0017, 1909.

1,024,839. Patented Apr. 30, 1912.

W". j avkfliar 1 w- "wi zw UNITED STATES PATENT OFFICE.

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Specification of Letters latent. I Patented-Apr. 1912f;

Application filed January 3, 1907, Serial No. 350,647. Renewed October 7, 1909. Serial N0. 521,490.

To all whom it may concern" Be i lmown that I, THOMAS ALVA Emsorr, a citizen of the United States, residing at Llewellyn Park, Orange, in the cou'nty'of Essex and State .of New Jersey, have in} vented acertain new and useful Improvewhich the following is a description.

My invention relates to an improved phonographic recording stylus,'a1id my object is to provide a device for thepurposein which a-very perfectcurved cutting edge can be formed of very small diameter. 1

At the present timethe available path on the blank for the accommodation of the record is one one-hundredth of an inch .01), since this is the standard pitch originally proposed by me and now adopted universally by talking machine manufac turers. The-recorders at present used pre; sent a substantially circular cutting edge the diameter of which is about four one-hundredths of an inch (.04). I now propose to make phonograph records with a pitch of two hundred threads per inch, the advantages' of which are explained in an'application for Letters Patentfiled on even date herewith. l In inder toform a record in a path onehalf as wide as that'now presented, and of the same depth asthat now formed, the recording stylus should not, as might be 'sup-' posed, be one-half the diameter, but it is necessary that it should be substantially onefourth" the diameter of that now einployed', namely, about oneonehundredth'of an inch.

'Even, in the manufacture of a recording stylus four one-hundredths of an inch in diamet'er the operation is a difficult one, requiring 'Iaborof the highest'skill, machines of great delicacy of adjustment and con-- struction, and most of the operations,have I tobe performed underthe microscope. Yet With these precautions there is very considerable loss by breakage, since the material used, sapphire, although extremely hard, is very brittle and of little bodily strength, so

that it chips and cracks readily. To attempt to form a recording st lusonly" one on'e-hundredth ofan-inch'in iameter of this material by present processes and machines, and

of the present type or form, might be possibIeas a mechanical phenomenon, but I do -not,believe it can ever'be done in a com;

a cutting edge of'smaller diameter and at the same time its shape will be such that the production of sharp angles is avoided, and ment in Plionographic Recording-Styli, of

sufficient material always presented to reduce cracking .or chipping to a minimum.

My improved recording stylus comprisesa shank on the end of which is formed a circular or"parti-circular head somewhat like the head of a pin, whose periphery pr'esents in cross section theproper curve for the cutting edge, and the head is cut away or notched to result" in the production of a cutting edge somewhat similar to that employed on an enormously larger scale in a shape tool. The stylus so obtained is mounted in a suitable socket so that the cutting edge will be. properly presented to the blank, and is carried by. or aflixed to the diaphragm in any suitable way. In order that the invention may be better understood, attention is directed to the accompanying drawings forming part of this specification, and in which-=- Figure 1 is a-sectional view on the line 1"'1 of Fig. 3, at the cutting edge of the improvedstylus showing the same greatlvenlarged,-and illustrating bydotted lines the relative shape of recorders now used having a diameter of four one-hundredths of an inch; Fig. 2, a perspective view of the-im;

proved stylus enlarged to one-fourth the scale of Fig. 1; Fig. 3, a front view of the same on the same scale at Fig. 2, and showing the stylus engaging a blank; Fig. 4, an end View of the stylus on a smaller scale, showing the same mounted on a diaphragm;

. Fig. 5, a front view-of the same, and Fig. 6

a planjviewof the same.

In these views corresponding parts are represented by-the same numerals of reference.

abl of sapphire. It is formed 'with a shank say, about nine one-hundredths of an inch.

The stylus, as heretofore, is made prefer 1 a out five one-hundredths' of an inch in -.'diaineter and of any. suitable-length, say, I i ,At 'itsfend it is turned with a button shaped head-2 of, somewhat larger diameter,

As shown in Fig. 1, this head is tapered to- V ward'its peripheryso as to make a strong andreadily formed construction which can he produced in a small lathe. The periphcry of the head 2 is formed with a curve ting edge 4 which can be done by a suitable rotating, tool. In forming this notched or cut-away portion the material is not removed at the angle thereof, but a curve is presented (see Fig. 3) to reduce to a minimum chipping or breaking in this operation. In mounting the improved stylus, the shank 1 is received and tightly secured by cement,

or otherwise, in a suitable socket. 5, which may be carried by a light frame 6 cemented to the diaphragm 7. -It will be obvious that my improved recording stylus, although it presents a cutting edge of'extremely small diameter, does not involve operations any more delicate than those now performedin making a stylus which is 'in fact four times as large, and at the same time the material is so disposed that there. is no greater danger of cracking or breaking than in the manufacture of a stylus of the existing standard.

In Fig. 1, I illustrate diagrammatically a; comparison between my improved stylus whose cutting edgepresents substantially a circle one one-hundredth of an inch in diameter, and a stylus as now constructed whose cutting edge "presents a circle four one-hundredthsof an inch in diameter. It will be seen that although the former is only about one-fourth the diameter of the latter, yet

in" cutting to the same depth it occupies one-half the width of the blank.

Having now described my invention what I claim as newand desire to secure by Let ters Patent, is as follows:

1. A recording stylus comprising a disklike head having a curved periphery formed with a notch therein to'present a cutting edge, the plane surface of which is transverse to the plane of said periphery, sub- 2. A recording styluscomprising a disklike head with a notch cut in said head said notch being formed with two converging substantially plane. surfaces connected by a curved surface, substantially as set'forth.

3. A recording stylus comprising. a shank and a disk-shaped head increasing in thickness from its periphery toward its center and formed with, a notch presenting a curved cutting edge, substantially as set forth. v

4. A recordin stylus consisting of ajewel having a roun ed periphery and formed with a notch which presents a substantially circular cutting edge having a diameter of less than two one-hundredths of an inch, substantially as set forth.

5. A recording stylus, consisting of a jewel formed with a shank and a disk-shaped head which increases in thickness from its periphery toward its center, said headbeing formed with a'notch which presents a substantially circular cutting edge having a diameter of less than two one-hundredths of an inch, substantially as set forth.

This specification signed and witnessed this 28th day of December 1906.

THOS. A. EDISON. Witnesses: 4

'FRANK L.-DYER,

ANNA R. KLEHM. 

